Have this on my wife's iPhone and see it's recently released for Android. Download from the Expansys website (curious there is no download from Navmii, the developers website!).
On the iPhone it worked well on a recent cross country trip. Ireland and UK maps are provided for free, with the option of purchasing maps for other countries. Have installed on my Galaxy S but haven't got the chance to use yet.
First impressions it looks very similar to iPhone version. Voices are sampled so sound a lot better than Google Navigation, but does not do text-to-speech. Considering the way Google murders Irish street names, this may be an advantage!!
Obviously the USP compared to Google Nav is that the maps are onboard, rather than using up data allowance, or roaming data when abroad.